Khaula Shirin, Sheraz Shafiq, Syed Arif Kazmi, Saima Imad, Mahroze A Khan.
Development of in-house standard reference material for estimation of metals in whole blood.
Pak J Med Res Jan ;54(1):29-33.

Objective: To develop the standard in order to assure that a test run is valid and results are reliable and the shelf life of the reference material will be at least six months. Study type, settings and duration: Quantitative analysis of metals in clinical samples PCSIR Laboratories, Karachi during six months. Materials and Methods: For this purpose 500ml human blood sample, obtained from blood bank was used to make a reference solution. This solution was prepared by acid digestion. After diluting to an appropriate volume, working solutions were freshly made and calibrated for each metal using the method of standard addition after a certain interval of time. E. Merck stock standards of 1000mg/l, were used for each metal to make the standard addition solutions. Percentage recoveries of standard addition solutions were calculated using the standard formula. Results: The analysis showed that the recoveries of most of the metals for both flame and graphite furnace were found to be within 4% of the actual values. The estimation of elements after an interval of about six weeks (four times) did not showed any difference from the intial concentration. This indicates the reproducibility of the results of metals was satisfactory. Similarly the internal spiking also showed the accuracy and comparability of the results. Conclusion: The prepared reference blood solution can be stored at ambient temperature and used as a reference standard at least for 6 months without change in the concentration of metals. It may be used as reference material if certified reference material is not available.

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